Start by identifying your bake type (cookies/quick breads vs. cakes vs. crusts) and choose the substitute that matches desired crumb (structure vs tenderness).
Measure by the listed ratio (1:1 or the reduced amount). For reduced-amount flours (like whole wheat), expect batter to be drier at first.
Adjust hydration: if batter looks stiff, add 1–2 teaspoons liquid at a time; if it looks too loose, add 1 tablespoon flour and reassess.
Rest when possible (especially with whole wheat and oat flour) for 5–10 minutes so the flour hydrates evenly.
Bake and evaluate: dense or gummy bakes often need slightly less flour, while crumbly bakes often need a binder or a touch more liquid.